Generally, a reciprocating compressor can be divided into a compressor which compresses and discharges the sucked gas by changing a rotating movement of a driving motor into a reciprocating motion of a piston, and a compressor which compresses and discharges the sucked gas by making the piston undergo reciprocating movement while the driving motor undergoes linear reciprocating movement.
FIG. 1 is a transverse cross-sectional view showing an embodiment of the reciprocating compressor in which the driving motor undergoes the linear reciprocating movement.
As shown therein, a conventional reciprocating compressor comprises a shell 10 in which a suction pipe (SP) and a discharge conduit (DP) are communicated with each other; a reciprocating motor 20 fixed inside the shell 10; a compressor unit 30 installed inside the reciprocating motor 10, sucking, compressing, and discharging gas; a frame unit 40 supporting the reciprocating motor 20 and the compressor unit 30; and a spring unit 50 elastically supporting an armature 22 of the reciprocating motor 20 in motion direction and guiding a resonance.
The reciprocating motor 20 includes a stator 21 including an inner stator 21A and an outer stator 21B, and an armature 22 disposed in a gap between the inner stator 21A and the outer stator 21B and undergoing a reciprocating movement.
The compressor unit 30 comprises a piston 31 coupled to a magnet supporting member 22A of the reciprocating motor 20 and undergoing the reciprocating movement together with the magnet supporting member 22A; a cylinder 32 fixed on a front frame 41 which will be described later, and forming a compressing space with the piston; a suction valve 33 installed on front end of the piston and restricting the suction of gas by opening/closing a gas passing hole 31b of the piston which will be described later; and a discharge valve assembly 34 disposed on the front end of the cylinder 32, whereby covering the compressing space, and restricting the discharge of compressed gas.
An inner flowing passage 31a communicating with the suction pipe (SP) is formed to a certain depth inside the piston 31, and the gas passing hole 31b communicated with the inner flowing passage 31a and penetrated to front end surface of the piston 31 is formed.
The frame unit 40 includes a front frame 41 contacting to front surfaces of the inner stator 21A and of the outer stator 21B, whereby supporting the stators together, and in which the cylinder 32 is inserted; a middle frame 42 contacting to rear surface of the outer stator 21B, whereby supporting the outer stator 21B; and a rear frame 43 coupled to the middle frame 42 and supporting rear end of a rear spring 52 which will be described later.
The spring unit 50 includes front spring 51 having both ends supported by the front surface of coupled part of the magnet supporting member 22A and the piston 31 and by the corresponding inner surface of the front frame 41, and a rear spring 52 having both ends supported by rear surface of the coupled part of the magnet supporting member 22A and the piston 31, and by corresponding front surface of the rear frame 43.
Reference numeral 22B designates a magnet.
The conventional reciprocating compressor as described above is operated as follows.
That is, when an electric current is applied to the winding coil 21C installed on the outer stator 21B of the reciprocating motor 20 and a flux is generated between the inner stator 21A and the outer stator 21B, whereby the armature 22 located in the gap between the inner stator 21A and the outer stator 21B moves in accordance with the direction of the flux and undergoes reciprocating movement by the spring unit 50. And accordingly, the piston 31 coupled to the armature 22 undergoes reciprocating movement inside the cylinder 32, so that a volume variance is generated inside the compressing space, accordingly the refrigerant gas is sucked into the compressing space, then compressed and discharged.
The refrigerant gas is sucked inside the shell 10 through the suction pipe (SP) during the suction stroke of the piston, and the gas is sucked into the compressing space of the cylinder 32 as opening the suction valve 33 through the inner flowing passage 31a of the piston 31 and through the gas passing hole 31b. Then, the gas is compressed to a certain level during the compress stroke of the piston, and discharged through the discharge conduit 34 as opening the discharge valve assembly 34. And the whole process is repeated.
However, in the conventional reciprocating compressor as described above, the refrigerant gas sucked into the shell 10 through the suction pipe (SP) is dispersed inside the shell 10, whereby the density per unit volume is lowered. Accordingly, the actual amount of refrigerant gas sucked into the compressing space during the reciprocating movement of the piston 31 is low, whereby the efficiency of the compressor is lowered.
Also, the refrigerant gas sucked into the shell 10 is pre-heated by contacting to the reciprocating motor 20 inside the shell 10, and then the gas is sucked into the compressing space. Therefore, the specific volume of the refrigerant gas is increased, and the performance of the compressor is lowered.
Also, when the suction valve 33 is opened/closed, the suction valve 33 is impacted to the front end surface of the piston 31, whereby the impact noise generated thereof is transferred to inside of the shell 10 entirely, and the noise of the entire compressor is increased.
In addition, when the suction valve 33 is opened/closed, the counter-flowing refrigerant gas is impacted with the sucked refrigerant gas instantaneously, whereby a pressure pulsation is generated. And the pressure pulsation is transferred to the suction pipe (SP) through the inner flowing passage 31a of the piston 31, and thereby the suction of the refrigerant gas is disturbed and the efficiency of the compressor is lowered.